Obesity and Cancer Risk in Young Adults in Korea : A Nationwide Health Screening Cohort Study.

Class I and class II obesity (BMI) in Korean adults aged 20–39 is linked to higher early-onset cancer risk over 11.2 years, with 10-year incidence rising to 2.24% and 2.62%.

• Why it matters: Obesity and early-onset cancer are increasing in young adults, but evidence on how obesity relates to incident cancer risk in this age group is limited.
• What they did: In a nationwide Korean National Health Insurance Service cohort (2009–2021; 6,313,338 cancer-free adults aged 20–39), BMI was grouped by Asian-specific criteria and followed for incident cancer (151,893 cases).
• The result: Ten-year cumulative incidence increased from 1.84% (normal weight) to 2.24% (class I) and 2.62% (class II), with larger absolute differences in women; abdominal obesity with class I BMI showed higher incidence (2.45% vs 2.13%).